Casing mill, method, and system

ABSTRACT

A mill for a single casing string including a housing, a first blade section having a blade of a first profile disposed in the housing and positionable to axially mill the single casing string, a second blade section having a blade of a second profile disposed in the housing and positionable to axially mill the single casing string, the first and second blades deployable simultaneously, the second blade configured to ride on an inside diameter surface of the single casing string while the second blade in the deployed position.

BACKGROUND

In the resource recovery and fluid sequestration industries, there is often need to mill casings. Tools exist for such activities but are lacking in efficiency and require costly construction. One particular prior art tool is that disclosed in U.S. Pat. No. 10,267,111 ('111). The subject of the '111 patent is a product commercially available from Baker Hughes under the product name Heavy Metal Section Mill. The tool uses two blades but the second is not deployed. Rather it is restrained in an undeployed position with a complex restraint configuration that increases cost of the tool. While the tool works as intended, the additional cost in its manufacture is undesirable. Since efficiency in cost as well as function is extremely important to operational profitability, the industry will well receive improved mills, methods, and systems.

SUMMARY

An embodiment of a mill for a single casing string including a housing, a first blade section having a blade of a first profile disposed in the housing and positionable to axially mill the single casing string. a second blade section having a blade of a second profile disposed in the housing and positionable to axially mill the single casing string, the first and second blades deployable simultaneously, the second blade configured to ride on an inside diameter surface of the single casing string while the second blade in the deployed position.

A method for milling a single casing string including rotating a mill having a first blade and a second blade, wherein both the first blade and the second blade are rotating and deployed, axially milling the casing string with the first blade, and contacting an inside diameter surface of the casing with the second blade without milling through the casing with the second blade.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:

FIG. 1 is a side view of a casing mill as disclosed herein in a run in position;

FIG. 2 is a cross sectional view of FIG. 1 ;

FIG. 3 is an enlarged view of either housing of FIG. 1 ;

FIG. 4 is a side view of a first blade of the casing mill of FIG. 1 ;

FIG. 5 is a side view of a second blade of the casing mill of FIG. 1 ;

FIG. 6 is a view of the casing mill of FIG. 1 in a deployed position and in a state of partial milling of the casing; and

FIG. 7 is a view of a wellbore system including the casing mill as disclosed herein.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.

Referring to FIGS. 1-3 a single casing mill 10 is illustrated, with FIG. 3 providing a close up view of either of the housing sections (they are the same). The mill 10 comprises a first housing 12 having a first blade section 18 and a second housing 16 having a second blade section 14. Housing 12 and housing 16 are connected together to create an assembly within which a hydraulic flow path 20 is maintained such that hydraulic fluid pressure may be applied to both the first and second blade sections 14 and 18 simultaneously. Such pressure is employed to deploy the blades for milling as will be understood by one of skill in the art.

Each of the first blade section 18 and second blade section 14 comprise different blades 22 and 24, respectively. The blades are different in their geometries to provide for different functions. While blades 22 and 24 are referred to individually, herein, in embodiments, each of these sections has a plurality of blades. Examples include 2, 3 or 4 blades but other numbers of blades may be substituted as desired. Referring to FIG. 5 , the first blade 22 is illustrated alone. The profile for blade 22 is configured to mill radially such that it is capable of opening a window and then also mills axially to longitudinally extend a window. Referring to FIG. 4 , in contrast, the profile of blade 24 is not intended to mill radially but rather only to mill axially in a preexisting window. The profile of blade 24 has been previously used in the art to avoid radially damaging a second casing section in a nested casing configuration. Specifically, where a 9-⅝ casing is disposed within a 13-⅜ casing and the 9-⅝ casing must be milled without damaging the 13-⅜ casing, the profile of second blade 24 would be used. The geometry was designed to protect the 13-⅜ casing from damage when the mill being used was of center, usually due to being located in a deviated section of well. With the relatively low contact pressure of the tool being off axis rather than the tool actively applying force to the blade, the geometry did what it was supposed to do. It was not, however, designed to protect a casing under the load that is applied to a blade when actuated against a casing that is to be milled. Surprisingly, the present inventors discovered that the geometry of the second blade 24 would also protect the casing even when loaded for milling. This discovery led to the understanding that in a two-blade mill system like that described herein, both blades could be deployed rather than requiring that the second blade be retained as taught in U.S. Pat. No. 10,267,111. The result is that a less expensive assembly may be employed and still achieve desirable results. With reference to FIG. 6 , the tool 10 is illustrated in a position where both blades 22 and 24 are deployed for milling. Blade 22 has milled radially through the casing 26 and blade 24 is riding on an inside surface 28 of the casing 26. Both blades 22 and 24 are fully loaded hydraulically when in this position. Subsequent to blade 22 cutting a long enough window to span both blades 22 and 24, the tool 10 is lowered to allow blade 24 to deploy through window 27 to its milling position to elongate the window 27.

Referring to FIG. 7 , a wellbore system 30 is illustrated. The system 30 comprises a borehole 32 in a subsurface formation 34. A string 36 is disposed within the borehole 32 and a casing mill 10 is disposed within or as a part of the string 36.

Set forth below are some embodiments of the foregoing disclosure:

Embodiment 1: A mill for a single casing string including a housing, a first blade section having a blade of a first profile disposed in the housing and positionable to axially mill the single casing string. a second blade section having a blade of a second profile disposed in the housing and positionable to axially mill the single casing string, the first and second blades deployable simultaneously, the second blade configured to ride on an inside diameter surface of the single casing string while the second blade in the deployed position.

Embodiment 2: The mill as in any prior embodiment wherein at least one of the first blade section and the second blade section includes a plurality of blades.

Embodiment 3: The mill as in any prior embodiment wherein the housing is a first housing supporting the first blade and a second housing supporting the second blade, the first and second housings being connected to one another to create a fluid pathway to both the first and second housings whereby both first and second blade are actuable by the same hydraulic pressure event.

Embodiment 4: The mill as in any prior embodiment wherein the first and second blade are rotated in the deployed position simultaneously.

Embodiment 5: The mill as in any prior embodiment wherein the first blade is configured to mill radially and axially.

Embodiment 6: The mill as in any prior embodiment wherein the second blade during use is restrained from full radial deployment only by the inside diameter surface of the casing string in which the mill is run.

Embodiment 7: A method for milling a single casing string including rotating a mill having a first blade and a second blade, wherein both the first blade and the second blade are rotating and deployed, axially milling the casing string with the first blade, and contacting an inside diameter surface of the casing with the second blade without milling through the casing with the second blade.

Embodiment 8: The method as in any prior embodiment wherein the rotating the first blade includes opening a window in the casing.

Embodiment 9: The method as in any prior embodiment wherein the axial milling with the first blade is continued until the first blade is worn.

Embodiment 10: The method as in any prior embodiment wherein the second blade automatically extends radially outwardly when it reaches the window.

Embodiment 11: The method as in any prior embodiment wherein the second blade axially mills the casing after the first blade is worn to extend the window longitudinal length.

Embodiment 12: A wellbore system including a borehole in a subsurface formation, a string in the borehole, and a mill as in any prior embodiment disposed in or as a part of the string.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Further, it should be noted that the terms “first,” “second,” and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms “about”, “substantially” and “generally” are intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. For example, “about” and/or “substantially” and/or “generally” can include a range of ±8% or 5%, or 2% of a given value.

The teachings of the present disclosure may be used in a variety of well operations. These operations may involve using one or more treatment agents to treat a formation, the fluids resident in a formation, a wellbore, and/or equipment in the wellbore, such as production tubing. The treatment agents may be in the form of liquids, gases, solids, semi-solids, and mixtures thereof. Illustrative treatment agents include, but are not limited to, fracturing fluids, acids, steam, water, brine, anti-corrosion agents, cement, permeability modifiers, drilling muds, emulsifiers, demulsifiers, tracers, flow improvers etc. Illustrative well operations include, but are not limited to, hydraulic fracturing, stimulation, tracer injection, cleaning, acidizing, steam injection, water flooding, cementing, etc.

While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. 

What is claimed is:
 1. A mill for a single casing string comprising: a housing; a first blade section having a blade of a first profile disposed in the housing and positionable to axially mill the single casing string; a second blade section having a blade of a second profile disposed in the housing and positionable to axially mill the single casing string, the first and second blades deployable simultaneously, the second blade configured to ride on an inside diameter surface of the single casing string while the second blade in the deployed position.
 2. The mill as claimed in claim 1 wherein at least one of the first blade section and the second blade section includes a plurality of blades.
 3. The mill as claimed in claim 1 wherein the housing is a first housing supporting the first blade and a second housing supporting the second blade, the first and second housings being connected to one another to create a fluid pathway to both the first and second housings whereby both first and second blade are actuable by the same hydraulic pressure event.
 4. The mill as claimed in claim 1 wherein the first and second blade are rotated in the deployed position simultaneously.
 5. The mill as claimed in claim 1 wherein the first blade is configured to mill radially and axially.
 6. The mill as claimed in claim 1 wherein the second blade during use is restrained from full radial deployment only by the inside diameter surface of the casing string in which the mill is run.
 7. A method for milling a single casing string comprising: rotating a mill having a first blade and a second blade, wherein both the first blade and the second blade are rotating and deployed; axially milling the casing string with the first blade; and contacting an inside diameter surface of the casing with the second blade without milling through the casing with the second blade.
 8. The method as claimed in claim 7 wherein the rotating the first blade includes opening a window in the casing.
 9. The method as claimed in claim 7 wherein the axial milling with the first blade is continued until the first blade is worn.
 10. The method as claimed in claim 8 wherein the second blade automatically extends radially outwardly when it reaches the window.
 11. The method as claimed in claim 7 wherein the second blade axially mills the casing after the first blade is worn to extend the window longitudinal length.
 12. A wellbore system comprising: a borehole in a subsurface formation; a string in the borehole; and a mill as claimed in claim 1 disposed in or as a part of the string. 